Carton



Oct. 22, 1957 P. G. SAUNDERS CARTON Filed Oct. 19, 1954 INVENTOR I fl/z/p 602010685 United States PatentO CARTON Philip G. Saunders, Toledo, Ohio, assignor to Owens- Illinois Glass Company, a corporation of Ohio Application October 19, 1954, Serial No. 463,085

4 Claims. (Cl. 229-37) This invention relates to an improved adhesively-sealed carton and method of sealingsame, by which the effort, annoyance, and destruction of the flaps customarily involved in opening such cartons is substantially reduced.

Cartons of corrugated paper or similar paper compositions have long been manufactured with two pairs of side and end flaps at both the top and bottom of the carton, which are respectively folded into abutting relationship and secured in such relationship to seal the carton by the application of a layer of suitable adhesive or glue between the abutting surfaces. Customarily, the side flaps of such cartons are of greater longitudinal dimensions than the width of the end flaps, so that when such flaps are sealed, the central portion of each side flap overlies a space between the free edges of the two end flaps. It is, therefore, customary to attempt to open such cartons by grasping the unsealed central portion of the side flap and pulling the side flap outwardly and upwardly with respect to the end flaps, to sever the adhesive bond between the side flap and the end flaps.

In such conventional carton constructions, it has been a common practice to provide a continuous adhesive bond between all abutting areas of the side and end flaps. Such bond is generally as strong as the flap material, so that substantial manual efiort is required to effect the severance of the side flap from the bonded end flaps, and it is not uncommon for the central portion of the side flap to merely tear out without eifecting a complete severance of the adhesive bond. As a result, it is practically impossible to complete the opening of the carton without the use of'either a knife or substantial manual effort.

It has heretofore been suggested, for example, in the patent application of Robert E. Graham, Serial No. 446,368, filed July 28, 1954, and assigned to the assignee of this application, that the manual etfort involved in opening such adhesively-sealed cartons may be substantially reduced by utilizing an adhesive bond in the form of spaced zones of adhesive. This invention constitutes a further improvement over the concept disclosed and claimed in the aforementioned Graham application;

It is an object of this invention to provide an improved carton construction and method for sealing such carton by which it is assured that the side flap of the carton may be torn loose from the adhesively-bonded end flaps with a minimum of manual effort and a minimum risk of tearing the side fiap in the process of breaking the adhesive bond.

A particular object of this invention is to provide a method of adhesively-sealing the side and end flaps of a carton characterized by the utilization of spaced zones of adhesive, wherein such zones are disposed so as to be continuously subject to maximum shearing forces when the central portions of the side flap are manually grasped and an opening force applied thereto.

Still another object of this invention is to provide an improved carton construction wherein spaced zones of adhesive are utilized to effect the sealing of a side flap of the carton to an adjacent end flap, characterized by the location of such adhesive zones in a predetermined relationship to the successive paths of maximum shearing stress normally produced by the manual application of opening force to the side flap, and further characterized by a cyclic variation in the effective area of such adhesive zones, as the separation progresses, to permit more advantageous utilization of the momentum developed by the operator in the separating operation.

The specific nature of this invention, as well as other objects and advantages thereof, will become apparent to those skilled in the art from the' following detailed description, taken in conjunction with the annexed-sheets of drawings on which, by way of preferred example only, are illustrated two embodiments of this invention.

On the drawings:

Figure 1 is a perspective view of a conventionally sealed carton in the process of being manually opened and illustrating the successive lines of maximum separation stress produced between the side and end flaps of such carton by the opening operation.

Figure 2 is a plan view of the end flaps of a carton illustrating the theoretical approximation of the paths of successive lines of maximum shearing forces exerted between the side flap and such end flaps by the manual opening operation.

Figure 3 is a plan view of the end flaps of a carton having adhesive applied thereto in accordance with this invention.

Figure 4 is a view similar to Figure 3, but illustrating a modified arrangement of adhesive zones in accordance with this invention.

As shown on the drawings: a

It will be readily apparent to those skilled in the art that this invention can be applied to any conventional form of carton wherein an adhesive bond is utilized to effect the sealing of the side and end flaps of such carton. The invention can be applied equally well to seal either the bottom or top set of flaps of a carton, but, since most cartons are commonly opened from the top, and the bottom flaps are generally permitted to remain in their 'sealed condition, the invention will be illustrated and described in conjunction with the sealing of the top set of flaps of a carton.

Referring to Figure 1, a conventional paperboard carton 10 is illustrated having side walls 10a, end walls 10b, side flaps 10c, and end flaps 10d. The side flaps 10c are respectively folded into overlying relationship with respect to the end flaps 10d, and, in conventional methods of sealing such cartons, the abutting surfaces of the side and end flaps are treated with an adhesive, and a continuous adhesive bond is produced therebetween. The carton is conventionally manually opened by grasping the central portion of the side flaps 10s, as indicated by' the hand of the operator in Figure l, and exerting an upward and outward force on such central portion, which tends to shear the adhesive bond between the particular side flap 10c and the two cooperating end flaps 10d.

As a result of extensive tests, it has been observed that the maximum shearing forces exerted on such a continuous adhesive bond by the application of manual separating forces in the manner indicated in Figure 1, follow a substantially uniform pattern for each size of carton. The successive location of the path of maximum shearing forces which are effective between the side flap 10c and the two end flaps 10d as the separation operation proceeds may be conveniently determined by incrementally producing such separation and drawing lines along the suc- Patented Oct. 22, 1957 paths of maximum separation stresses produced between the side flaps and end flaps by the application of a manual separating force to the central portions of the side flaps. By the same token, the directiontof progression of the tear will be represented by lines 11a which are continuously perpendicular to successive lines 11.

I have discovered by repeated tests that such maximum stress paths as plotted on any particular end flap may be substantially approximated by a series of straight. lines across such end flap that are radial with respect to a point located along the fold line of the cooperating side flap and spaced from the center of such side flap in a direction away from the particular end flap by a distance equal approximately to' one-half the width of the human hand that is producing the separating forces. Thus, as illustrated in Figure 2, the straight lineslZ on each end flap 1001 are respectively radial about point 0, which is located along the fold line of the cooperating side flap and is spaced from the center of such side flap in the direction away from the particular end. flap by distance A, which is approximately one-half the width of the human hand. Therefore, the method of this invention contemplates the application of spaced zones of adhesive between the cooperating side and end flaps, each zone being located along a path of tearing progression, which paths constitute arcs 12a swung about point 0. The application of this method necessarily results in a substantial reduction in manual eifort required to effect the opening of the carton, since the manual force applied is most cfiiciently utilized to successively effect the severance of the successive adhesive bonds. This increase in shearing efiiciency may be better understood from the followmg:

Assume, first, that the entire abutting areas of a side flap and a particular end flap are adhesively' secured together; then, upon the operator grasping the central portion of the side flap in the manner indicated in Figure l, the effective shearing force that he exerts will be at one point distributed along the first ofthe successive paths of maximum shearing force, for example, the path 111) in Figure I. To effect the separation of the side flaps and end flaps along the path 11b with less force, it is necessary to reduce the total effective adhesive area of such path. This can be done by applying adhesive to only spaced portions of the total area provided by such path, such as indicated by the bands 110. For maximum cfliciency, the spaced bands or zones of adhesive 110 should progress across the abutting surfaces of the side flap and end flap in exactly the same direction as the separation tends to proceed. As indicated above, this direction is defined by lines 11a, which are continuously perpendicular to the successive lines 11 of maximum shearing stress. p

If any other configuration of adhesive zones is employed, for example, zones running parallel to one of the edges of the flaps, it will be apparent that the successive lines 11 of maximum shearing force will traverse such zones in angular relationship, and, hence, a greater amount of adhesive will be available along any one of the successive paths of maximum shearing force to resist such shearing force. Thus, the use of spaced adhesive zones constructed in accordance with this invention assures that any applied opening force will be opposed at anyone time by a minimum efiective area of adhesive.

Referring to Figure 3, there is shown a plurality of spaced adhesive zones 13, each of which is located along a path perpendicular to the successive lines of maximum shearing stress, such as the lines 11 of Figure 1 or the close approximation thereto provided by the straight lines 12 of Figure 2. It should be noted that once suflicient force is exerted to initiate the separating action, the hand of the operator doing the opening operation would. acquire a certain amount of momentum which would assist in subsequent separating. This momentum factor is more etficiently' utilized in the modification of this invention shown in Figure 4, wherein each adhesive zone 14 is again located along a path perpendicular to the paths of successive maximum shearing stress, but each zone comprises a plurality of discrete diamond-shaped sub-zone areas 14a so oriented that the separating force required to traverse any particular sub-zone cyclically increases from zero to a maximum and then back to zero. With this arrangement, once the operator exerts sutficient force to start the separation of the side fiap from the cooperating end flaps, the mo mentum he achieves after passing through the first adhesive sub-zones will carry him well into the next adhesive sub-zones, so that the entire separation operation will proceed without the operator being aware of any substantial increase in manual effort required on his part.

Any one of several methods for applying the adhesive in the particular zone patterns described herein may be utilized. The method that is most convenient and best suited to large quantity production of such cartons is to apply a coating of ink to either the abutting face of the side flap or its cooperating end flaps, such ink coating covering all areas of such flaps except the area constituting the adhesive zones. 7 It will, of course, be understood that the adhesive may be applied to either the undersurface of the side flap or the top surface of the end flaps; the only important requirement is the establishment of adhesive zones between the abutting faces of such flaps in the patterns herebefore described.

From the foregoing description, it should be apparent that this invention not only substantially reduces the manual effort required to open an adhesively-sealed carton by utilizing the manually applied forces in the most eificient manner, but also efiects a substantial reduction in the possibility of tearing the particular flap of the carton to which the opening force is applied. Thus, the carton may be readily reused and further economies achieved.

It will, of course, be understood that various details of construction or procedure may be modified through a wide range without departing from the principles of this invention, and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim:

1. In a carton having upper and lower integral closure flaps adapted to be folded into face-to-face abutment about their respective fold lines to close an end of the carton, the improvement of an adhesive layer on one of said flaps, said adhesive layer being discontinuous and consisting of a series of isolated adhesive areas, said areas being arcuately disposed about a common center located on the fold line of the upper flap, said center being the locus of successive paths of shear force generated upon application of force on the flaps by elevation of the center of the edge of the upper flap opposite its fold line about its fold line, and said areas lying substantially normal to lines radiating from said center and representing the paths along which maximum shear force is applied to said adhesive layer.

2. In a carton, a pair of integral, foldable upper and lower closure flaps having their opposing faces adapted to be' adhesively secured to one another by a discontinuous layer of adhesive therebetween, said layer consisting of individual bands of adhesive applied to one of the flaps in a pattern oriented with respect to the locus of the lines of maximumsepara'tion stress generated upon application of force on the flaps by elevation of the centerof the free edge of the upper flap'about its fold line, said locus lying on said fold line outside the confines of the lower flap, and said bands beingconcentric about said locus and each lying substantially normal to said lines of maximum separation stress.

3. In a carton having an upper side flap for adhesive attachment to a pair of lower end. flaps, a plurality of spaced'adhesive zones on at least one-of said flaps for joining the underface of said side flap to the upper faces of said end flaps, said adhesive zones on any one flap being arcuate and said zones on any one flap being centered at a point located along the fold line of said side flap, each of said points being displaced from the center of said side flap in a direction away from its particular end flap and through an appreciable distance from said side flap center.

4. In a carton having a side flap adapted to be adhesively secured to a pair of end flaps the free edges of which are spaced sufiiciently to accommodate the entry of a human hand therebetween, a plurality of spaced adhesive zones on at least one of said flaps for joining the underface of said side flap to the upper faces of said end flaps, the individual adhesive zones on any one flap being arcuate and the zones on each such flap being concentric about a point located along the fold line of said side flap, the point for a given end flap being located outside the confines of the given end flap and between the center of the side flap and the free edge of the other end flap.

References Cited in the file of this patent UNITED STATES PATENTS 1,103,177 Dye July 14, 1914 2,113,927 Alfred Apr. 12, 1938 2,133,946 Bloomer Oct. 25, 1938 2,162,556 Lagaard June 13, 1939 2,219,560 Maurin Oct. 19, 1940 2,281,304 Gillian Apr. 28, 1942 2,727,676 Tilly Dec. 20, 1955 2,745,592 Steck May 15, 1956 

